In some medical applications, it may be necessary to dynamically track targets that move with time. For example, in radiosurgery it may be desirable to dynamically track tumors and/or lesions in the human body that move with respiration and/or heartbeat. In radiosurgery, accurate trajectories of the radiation beams through the patient anatomy to the lesion or tumor being treated can be critical, in order to achieve the radiation dose distribution that was computed during treatment planning time. For regions of the human anatomy that move, for example due to breathing or heartbeat, it is important to take such motions into consideration, when computing the effect of the motion on the treatment plan being generated. Dynamic tracking may also be useful in applications other than radiosurgery in which parts of the anatomy move, due to breathing, heartbeat, or any other type of motion.
Fiducial markers have been used in the past, in order to track moving regions of the anatomy. Fiducials-based tracking can be difficult for a patient, for a number of reasons. For example, high accuracy tends to be achieved by using bone-implanted fiducial markers, but less invasive techniques such as skin-attached markers or anatomical positions tend to be less accurate. Implantation of fiducials into a patient is generally painful and difficult, especially for the C-spine, the implantation process for which may frequently lead to clinical complications.
In some methods that use gating to handle anatomical motion, dynamic tracking may be achieved by establishing a relationship between internally implanted fiducials, and externally placed markers that are tracked in real time. These methods do not take into account the non-rigid motions and deformations of the surrounding anatomy, as a function of the motion cycle.
A method and system that address these deficiencies are thus desirable. In particular, it is desirable to provide a reliable and efficient method and system for dynamically tracking moving targets.